I use the Ruby Version Manager gem, rvm, to work with multiple versions of Ruby on one computer. Rvm stores Ruby interpreters under /Users/username/.rvm, which makes those interpreters impossible to select. Paths beginning with a dot are filtered out of the folder listings in the Open dialog that appears after clicking "Add Platform...". Without the ability to traverse those paths, I cannot select my alternate Ruby installations.
I should note, however, that this was discovered during an attempt to see if I could use NetBeans with Ruby 1.9. If there's no Ruby 1.9 support, then resolution of my issue might not be worth the trouble.

You should be able to just type in the dot folder name in the open file dialog and click OK, then you can browse the contents of the folder. NB does support 1.9, let me know if this doesn't work for you - thanks!

The open file dialog I'm receiving does not include a text field. There's no place to actually type a path manually. At the top of the dialog, I have a dropdown to select steps along the parent path. Below that I have the folder listing, a two column table listing Name and Date Modified. Beneath that, I have a File Format drop down that only contains "Ruby Interpreter". There are no other controls present in the dialog except for the Cancel and Open buttons.